Economic and Environmental Geology (자원환경지질)

The Korean Society of Economic and Environmental Geology (대한자원환경지질학회)
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Fresh Water Injection Test in a Fractured Bedrock Aquifer for the Mitigation of Seawater Intrusion

해수침투 저감을 위한 균열암반 대수층 내 담수주입시험

  • Shin, Je-Hyun (Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources) ;
  • Byun, Joong-Moo (Department of Natural resources and Environmental Engineering, Hanyang University)
  • 신제현 (한국지질자원연구원 지구환경연구본부) ;
  • 변중무 (한양대학교 자원환경공학과)
  • Received : 2010.07.23
  • Accepted : 2010.08.20
  • Published : 2010.08.28
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Abstract

Fresh water injection test in a fractured bedrock aquifer was applied as an efficient approach to lower saline concentrations in the saltwater-freshwater transition zone formed by seawater intrusion in a coastal area. The methodology and effectiveness of fresh water injection for hydraulically controlling seawater intrusion is overwhelmingly site dependent, and there is an urgent need to characterize the permeable fractures or unconsolidated porous formations which can allow for seawater flow and transport. Considering aquifer characteristics, injection and monitoring boreholes were optimally designed and completed to inject fresh water through sand layer and fractured bedrock, respectively. We devised and used the injection system using double packer for easy field operation and maintenance. Overall fracture distribution was systematically identified from borehole image logs, and the section of fresh water injection was decided from injection test and monitoring. With fresh water injection, the fluid electrical conductivity of the monitoring well started to be lowered by the inflow of fresh water at the specific depth. And this inflow leaded to the replacement of the fluid in the upper parts of the borehole with fresh water. Furthermore, the injection effect lasted more than several months, which means that fresh water injection may contribute to the mitigation of seawater intrusion in a coastal area.

연안지역 염수와 담수가 혼재하는 전이대에서 해수침투 피해개선을 목적으로 균열암반을 통한 담수주입시험을 수행하고 그 효과를 모니터링하였다. 담수주입은 절대적으로 그 지역의 지질학적, 수리학적 특성에 따라 좌우되며, 특히 파쇄대나 투수성 미고결 지층 등의 특성 파악이 중요하다. 연구 지역의 염담수 분포특성을 고려하여 두 개의 주요 연안 대수층인 충적층과 균열암반 구간을 통한 담수주입이 가능하도록 시추공을 설계 및 굴착하였으며, 균열암반 대수층 내 담수주입을 위하여 현장에서의 시험 준비, 이동, 조립 및 장비의 유지보수가 간단하도록 착탈식인 모듈화되어 있는 주입시스템을 제작하여 적용하였다. 시추공영상화검층을 통해 전체적인 균열의 특성을 파악하였고, 이를 바탕으로 주입공 및 관측공 간 투수성 파쇄대의 확인을 위한 구간별 담수주입 및 모니터링을 실시하여 담수주입 구간을 선정하였다. 담수주입시험 결과, 관측공의 일정 심도에서 담수가 유입되어 시간이 경과함에 따라 상부 구간의 전기전도도도 점진적으로 감소함을 보였으며, 담수주입 중단 및 패커를 해지한 후에도 유입된 심도에서 점진적으로 전기전도도값이 증가하기는 하지만 그 증가폭이 전체적으로 낮아 담수주입의 효과가 있음을 확인하였다. 또한 장기적으로 전기전도도값을 모니터링함으로써 담수주입의 효과가 수개월 후에도 지속됨을 확인하였으며, 이는 담수주입에 의해 일정 정도의 해수침투 피해에 대한 개선효과를 기대할 수 있음을 시사한다.

Keywords

Acknowledgement

Grant : 지구환경변화 대응 지하수 확보 통합솔루션 개발

Supported by : 한국지질자원연구원

References

  1. Cohen, A.J.B., Karasaki, K., Benson, S., Bodvarsson, G., Freifeld, B., Benito, P., Cook, P., Clyde, J., Grossenbacher, K., Peterson, J., Solbau, R., Thapa, B., Vasco, D. and Zawislanski, P. (1996) Hydrogeologic characterization of fractured rock formations: A guide for groundwater remediators. United States Environmental Protection Agency, EPA/600/S-96/001, p.4-5.
  2. Hwang, S., Oh, H. and Song, M.-Y., (2008) Heat-pulse flowmeter test to characterize seawater intrusion in fractured rock, Yeonggwang area. Geosystem Engineering, v.45, p.1-14.
  3. Hwang, S., Park, Y., Shin, J. and Park, K.G. (2006) Detection of inflow permeable zones using fluid replacement conductivity logging in coastal aquifer. Geophysical Exploration, v.9, p.225-230.
  4. Hwang, S., Shin, J., Park, I. and Lee, S. (2004) Assessment of seawater intrusion using geophysical well logging and electrical soundings in a coastal aquifer, Youngkwang-gun, Korea. Exploration Geophysics, v.35, p.99-104. https://doi.org/10.1071/EG04099
  5. Hwang, S., Yun, S.T., Park, I., Shin, J., Shin, K.S. and Lee, S. (2003) Investigation for regional saltwater intrusion of western and southern coastal area in South Korea (Abstract). Proceedings of 80th Meeting of the Korean Society for Geosystem Engineering, 413p.
  6. Kim, Y., Kim, T., Kim, K.Y., Hwang, S. and Chae, B.G. (2005) Analysis of groundwater flow characterization in fractured aquifer system. The Journal of Korean Society of Soil and Groundwater Environment, v.10, p.33-44.
  7. Paillet, F.L. (2001) Hydraulic head applications of flow logs in the study of heterogeneous aquifers. Ground Water, v.39, p.667-675. https://doi.org/10.1111/j.1745-6584.2001.tb02356.x
  8. Park, K.G., Shin, J., Hwang, S. and Park, I. (2007) Fresh water injection test to mitigate seawater intrusion and geophysical monitoring in coastal area. Geophysical Exploration, v.10, p.353-360.
  9. Pyne, R.D.G. (1995) Groundwater recharge and wells: a guide to aquifer storage recovery. Lewis Publishers, 376p.
  10. Shin, J., Hwang, S., Park, K.G., Park, Y. and Byun, J. (2005) The development of multi-channel electrical conductivity monitoring system and its application in the coastal aquifer. Geophysical Exploration, v.8, p.156-162.
  11. USEPA (1999) Salt water intrusion barrier wells. United States Environmental Protection Agency, EPA/816-R-99-014t, p.22-27.
  12. Williams, J.H. and Johnson, C.D. (2004) Acoustic and optical borehole-wall imaging for fractured-rock aquifer studies. Journal of Applied Geophysics, v.55, p.151-159. https://doi.org/10.1016/j.jappgeo.2003.06.009